Pipette

Abstract

A pipette with a rod-shaped casing, a seat, a displacement equipment, comprising a displacement chamber with a relocatable limit, a connection channel, a drive equipment for relocating the relocatable limit of the displacement chamber, coupled to the relocatable limit and having an axially relocatable lifting rod, an upper stop body, a lower stop body and a stop element on the circumference of the lifting rod for limiting the stroke of the lifting rod, an overstroke spring, a stationary screw element, and with a screw element that is relocatable in the casing, a toothing, running along a helical line with the same pitch as that of the thread of the relocatable screw element and having teeth on the upper edge of the relocatable screw element that are directed in the direction of the instantaneous axis of the relocatable screw element, a toothed driving wheel, and means for rotating the toothed driving wheel.

The inventin claimed is: 
     
       1. A pipette with
 a rod-shaped casing ( 2 ,  3 ), 
 a seat ( 50 ) for detachably holding a pipette tip ( 51 ) on the lower end of the casing ( 2 ,  3 ), 
 a displacement equipment, comprising a displacement chamber ( 57 ) with a relocatable limit ( 58 ), 
 a connection channel ( 56 ), connecting the displacement chamber ( 57 ) with an opening in the seat, 
 a drive equipment for relocating the relocatable limit ( 58 ) of the displacement chamber ( 57 ), coupled to the relocatable limit ( 58 ) and having an axially relocatable lifting rod ( 6 ), 
 an upper stop body ( 8 ), a lower stop body ( 27 ) and a stop element ( 25 ) on the circumference of the lifting rod ( 6 ) for limiting the stroke of the lifting rod ( 6 ), 
 an overstroke spring ( 31 ), via which the lower stop body ( 8 ) is supported against relocation towards the downside on an overstroke spring support ( 32 ), 
 a stationary screw element ( 10 ), fixedly connected to the casing ( 2 ,  3 ), and with a screw element ( 92 ) that is relocatable in the casing and is engaged to the stationary screw element ( 10 ) and is coupled to the lower stop body ( 27 ) in order to relocate it in the axial direction of the lifting rod ( 6 ) when the relocatable screw element ( 92 ) is being relocated, 
 a toothing ( 95 ), running along a helical line ( 96 ) with the same pitch as that of the thread ( 93 ) of the relocatable screw element ( 92 ) and having teeth on the upper edge of the relocatable screw element ( 92 ) that are directed in the direction of the instantaneous axis of the relocatable screw element ( 92 ), 
 a toothed driving wheel ( 100 ), rotatably mounted on a bearing ( 97 ) that is fixedly connected to the casing ( 2 ,  3 ), and being engaged with the toothing ( 95 ) of the relocatable screw element ( 92 ), and 
 means ( 103 ) for rotating the toothed driving wheel ( 100 ). 
 
     
     
       2. The pipette according to  claim 1 , wherein the relocatable screw element ( 92 ) is a threaded ring, disposed concentrically to the lifting rod and having a thread ( 93 ) on the circumference, which has the toothing ( 95 ) at the topside and rests on the lower stop body ( 27 ) at the downside. 
     
     
       3. The pipette according to  claim 2 , wherein the stationary screw element ( 10 ) is a hollow cylindrical lifting body which has an external thread ( 91 ) at the outer circumference to which an internal thread ( 93 ) on the inner circumference of the threaded ring ( 92 ) is engaged, the lifting body ( 10 ) has several axially extending slots ( 89 ), the lower stop body ( 27 ) is arranged in the lifting body ( 10 ) and the lower stop body ( 27 ) has several outwardly projecting projections ( 29 ) which grip through the slots ( 89 ) and have portions that jut out of the lifting body ( 10 ) and on which the threaded ring ( 92 ) is seated. 
     
     
       4. The pipette according to  claim 3 , wherein the overstroke spring support ( 32 ) is disposed in the lifting body ( 10 ), and the overstroke spring ( 31 ) is disposed in the lifting body ( 10 ) between the lower stop body ( 27 ) and the overstroke spring support ( 32 ). 
     
     
       5. A pipette according to  claim 1 , wherein the upper stop body ( 8 ) is a threaded spindle which is screwed into a spindle nut ( 9 ) that is fixedly connected to the casing ( 2 ,  3 ), and which has an upper passage channel ( 7 ) through which the lifting rod ( 6 ) is guided, and/or the lower stop body ( 27 ) is circular disc shaped and has a lower passage channel ( 28 ) through which the lifting rod ( 6 ) extends. 
     
     
       6. The pipette according to  claim 5 , wherein the lifting body ( 10 ) is fixedly connected to the spindle nut ( 9 ) at the topside. 
     
     
       7. A pipette according to  claim 3 , wherein the bearing ( 97 ) of the toothed driving wheel ( 100 ) is fixedly connected to the lifting body ( 10 ) above the external thread ( 91 ). 
     
     
       8. A pipette according to  claim 1 , wherein the lifting body ( 10 ) is connected to the casing via a snap connection. 
     
     
       9. A pipette according to  claim 1 , wherein the stationary screw element ( 10 ) and the relocatable screw element ( 92 ) are bevel wheels or contrate wheels. 
     
     
       10. A pipette according to  claim 1 , which has an indicating equipment ( 92 ,  104 ,  106 ) for indicating the position of the lower stop body ( 27 ). 
     
     
       11. The pipette according to  claim 10 , wherein the threaded ring ( 92 ) has marks ( 104 ) at the outer circumference, spaced apart from each other in the circumferential direction, and the casing has a window ( 106 ) for reading a mark ( 104 ) that is disposed under the window ( 106 ). 
     
     
       12. The pipette according to  claim 11 , wherein the marks ( 104 ) on the circumference of the toothed drive wheel ( 100 ) are disposed on a further helical line ( 105 ), whose pitch corresponds to the pitch of the thread ( 93 ) of the relocatable screw element ( 92 ). 
     
     
       13. A pipette according to  claim 1 , wherein the toothed drive wheel ( 100 ) has a tool application device ( 103 ) for rotating the toothed drive wheel and the casing has a hole ( 107 ) through which the tool application device ( 103 ) is accessible my means of a tool that is introduced into the hole ( 107 ) from the outside. 
     
     
       14. A pipette according to  claim 1 , which has means for limiting ( 108 ) the rotation of the relocatable screw element ( 92 ), so that the highest tooth of the toothing ( 95 ) cannot disengage from the toothed drive wheel ( 100 ). 
     
     
       15. A pipette according to  claim 1 , wherein the toothing ( 95 ) of the relocatable screw element ( 92 ) is limited by an axial projection ( 108 ) next to the highest tooth, which blocks the toothed drive wheel ( 100 ) at the end of the axial toothing ( 95 ).